/*
 * Copyright 2006 Robert Burrell Donkin
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */ 
package rat.header;

import java.io.IOException;
import java.io.Reader;
import java.nio.CharBuffer;

class FilteringSequenceFactory {
    
    private static final int BUFFER_CAPACITY = 5000;
    
    private final CharBuffer buffer;
    private final CharFilter filter;
    
    public FilteringSequenceFactory(final CharFilter filter) {
        this(BUFFER_CAPACITY, filter);
    }
    
    public FilteringSequenceFactory(final int capacity, final CharFilter filter) {
        this.buffer = CharBuffer.allocate(capacity);
        this.filter = filter;
    }

    public CharSequence filter(Reader reader) throws IOException {
        buffer.clear();
        boolean eof = false;
        while(!eof) {
            final int next = reader.read();
            if (next == -1 || !buffer.hasRemaining()) {
                eof = true;
            } else {
                final char character = (char) next;
                if (!filter.isFilteredOut(character))
                {
                    buffer.put(character); 
                }
            }
        }
        buffer.limit(buffer.position()).rewind();
        return buffer;
    }
}
